The present invention relates to compositions and methods for treating, for example, cleaning, contact lenses. More particularly, the invention relates to particle-containing compositions useful for treating contact lenses, for example, to remove debris or deposit material from contact lenses.
Cleaning of contact lenses is desirable because of the tendency of material to deposit on the lenses. These deposits may include proteinaceous materials, lipids, as well as foreign matter, such as eye makeup, which can accumulate on the lens surface. Contact lens cleaning based solely on a chemical or solvent approach may have difficulty in affording deposit removal in a reasonable time and/or in removing all the deposit materials likely to be encountered. As an alternative, physically rubbing the lens with a cleaning composition may be advantageous.
A number of contact lens cleaning systems have been proposed which include a particulate component used to physically contact and clean contact lenses. For instance, Ishii et al, U.S. Pat. No. 5,128,058 describes a contact lens cleaner having microcapsules which reportedly assist in removing dirt or stains from a contact lens surface. The microcapsules are formed by laminating an inorganic polishing agent, such as silica, alumina, etc., onto a plastic core. A ball mill process is used whereby the inorganic agent is believed to adhere to the plastic due to frictionally generated electric charges on the plastic core. It is expected that the static electric charges which initially hold the laminated layer onto the plastic quickly dissipate, whereupon the formed particle either crumbles or stays together essentially as a plastic core surrounded by a substantially rigid inorganic shell. The outer shell of these particles is harder than the inner elastic core. It is likely that the hard outer surface of these particles disadvantageously causes significant scratching and/or wear of the contact lens surface coincident with removal of deposits from the surface.
Another cleaning agent proposed for use with hard and soft contact lenses is found in Suet al U.S. Pat. No. 5,037,484. This composition includes organic polymer or polysiloxane particles having a size between one and 600 microns suspended in a carrier, which usually contains a thickening agent. Due to the uniform elasticity or rigidity of these particles, depending upon the particular particle formation conditions, it is not likely that they can provide adequate scouring capacity when the particle is elastic or sufficient softness to avoid lens scratching when the particle is composed of a rigid polymer.
A further approach to a contact lens cleaning composition is proposed by Bhatia U.S. Pat. Nos. 4,921,630 and 4,839,082 which describe a chemical formulation that purportedly forms an abrasive precipitate, with or without the presence of an enzyme, upon the interaction of a carboxy vinyl polymer in the formulation with one or more substances on the surface of the lens. When an enzyme is present, the enzyme is believed to assist in the removal of protein deposits, and the like. It is difficult to control the formation and size of the precipitate particles to obtain adequate cleaning without damaging the lenses. The precipitate has uniform mechanical properties, for example, hardness and elasticity, throughout the particles.
Another cleaning composition that includes a particulate agent is described by Chromecek et al U.S. Pat. No. 4,655,957. This composition contains a particulate hydrophilic polymer or copolymer, which reportedly attracts lens deposits from the lens surface. These polymers are described as being in the form of solid beads. The composition, hardness and elasticity of the beads apparently can be modified with a "modulus modifier," which is added to the reaction mixture prior to bead formation and therefore is uniformly dispersed in the beads. Again, when a cleaning particle having an elastic surface is desired in order to avoid lens scratching, the entire particle must be elastic because of the bead formation process. This inherent property of these particles reduces their effectiveness in removing deposits from a lens surface.
It would be advantageous to provide an effective contact lens cleaning system which both effectively removes deposit material from the lenses and avoids detrimental abrasion or scratching of the lenses.